[PATCH] autofs4: add v5 follow_link mount trigger method

This patch adds a follow_link inode method for the root of an autofs direct
mount trigger.  It also adds the corresponding mount options and updates the
show_mount method.

Signed-off-by: Ian Kent <raven@themaw.net>
Cc: Al Viro <viro@ftp.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>